The present disclosure relates to a power amplifier module. In mobile communication terminals, such as cellular phones, a power amplifier circuit is used to amplify the power of a signal to be transmitted to a base station. In recent years, modulation schemes, such as high speed uplink packet access (HSUPA), long term evolution (LTE), and LTE-Advanced, which are high-speed data communication standards, have been adopted in cellular phones. In such communication standards, it is important to reduce a phase shift and an amplitude deviation to increase communication speeds. That is, high linearity is demanded for the power amplifier circuit. Furthermore, in such communication standards, a range (dynamic range) in which the amplitude of a signal changes is widened to increase communication speeds in many cases. To achieve high linearity even in the case of a large dynamic range, a high power-supply voltage is necessary, and the power consumption of the power amplifier circuit tends to increase. Thus, a power amplifier module employing an envelope tracking technique has been studied that promotes an improvement in power gain by controlling a power-supply voltage of the power amplifier circuit in accordance with an amplitude level of an input modulated signal.
In a power amplifier module used in a mobile communication terminal that is driven by a battery, a reduction in power consumption is demanded, whereas power gain with high linearity based on a communication scheme is demanded. For example, Japanese Patent No. 5958483 discloses a power amplifier module employing an envelope tracking technique. The power amplifier module includes, as a matching network for first and second power amplifier circuits, first and second capacitors connected in series with each other, and an inductor connected between a point between the first and second capacitors and a ground.
In general, as a frequency of a signal to be amplified increases, element values of a capacitor and an inductor that are necessary for a matching network decrease. For this reason, when a frequency of an input signal is high, large variations in characteristics of the matching network are caused by variations in the element values of the capacitor and the inductor. Thus, impedance mismatching between matching networks occurs, thereby raising the possibility of a reduction in power gain.